A video on YouTube shows the 20-year-old Ward walking along the race track after he and Stewart collided, sending Ward into the retaining wall. As Stewart approaches, Ward gestures to Stewart, whose car hits Ward.

Authorities described Stewart as "visibly shaken" after the crash and said he was cooperative. On Sunday, Ontario County Sheriff Philip Povero said criminal charges have not been ruled out but that investigators also don't have any evidence at this point in the investigation to support criminal intent.

The crash happened Saturday night at Canandaigua Motorsports Park, a dirt track and an extracurricular race for a driver of Stewart's stature. Stewart frequently races in the events as a hobby to the side of the big-money NASCAR races. Stewart pulled out of his scheduled NASCAR race Sunday at Watkins Glen.

Here is a YouTube video showing the crash. Be advised of its graphic nature: